KR20160013038A - Method for conveying a metered hydraulic volume in a vehicle braking system by means of an electrically driven motor pump assembly and vehicle braking system - Google Patents

Abstract

The present invention relates to a method of transferring a metering hydraulic volume in an automotive braking system by means of an electrically driven motor pump assembly wherein the mechanical pump of the motor pump assembly is driven by an electric motor of the motor pump assembly. The motor current 12 is detected and the motor torque generated by the motor current 12 is added to the sum of the drag torque, the brake away torque, and the friction torque of the motor pump assembly As soon as it is exceeded, the delivery mode of the motor pump assembly begins. The motor current 12 decreases when the transfer mode starts. The method is characterized in that the motor voltage (11) is reduced to a value which terminates the delivery mode when a decrease in the motor current (12) is detected after a specified time interval has elapsed. The present invention also relates to a vehicle braking system.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of transporting a metering hydraulic volume in a vehicle braking system by means of an electrically driven motor pump assembly and a vehicle braking system. }

The present invention relates to a method of delivering a metering hydraulic volume in a vehicle braking system by means of an electrically driven motor pump assembly according to the preamble of claim 1 and a vehicle braking system according to the preamble of claim 10.

An anti-lock braking system, a travel stability control system, a distance control system, or an anti-rollover system for braking-related comfort and safety systems of motor vehicles, for example, antilock braking systems, Sensitive control. However, as a prerequisite for the correspondingly sensitive control, it should also be possible to control the pump motor of the hydraulic braking system according to the corresponding precision. Particularly sensitive control is usually achieved by a pulse width modulated current signal, where the current signal is preferably modulated at a frequency of up to 18 kHz. However, it is likewise possible to modulate the current signal at a frequency in excess of 18 kHz. In general, the greater the frequency of modulation, the more sensitive the pump motor is to operate. It is also usually necessary that the specific angular position of the motor or pump be known as precisely as possible.

In this context, DE 10 2009 006 891 A1 discloses an electric motor for a hydraulic pump in a braking control system. The electric motor comprises a rotor connected to the motor shaft, and a stator having a plurality of brushes, wherein the rotor provided with turns comprises a commutator having a plurality of commutator bars. In order to allow accurate detection of the rotational angular position of the motor shaft, one of the commutator bars is longer than the remaining commutator bars. Also, one of the brushes has an axial offset to contact the elongated commutator bar. Thus, a signal characteristic of the rotational angular position can be sensed through the offset brush. Thus, since the actual rotational speed of the motor can be detected regardless of the torque applied, its speed can be corrected at any time to the desired setpoint value through the duty factor of the pulse width modulated control.

DE 10 2008 018 818 A1 describes an electric motor control method with load torque adaptation. In this case, the electric motor is controlled by a current source, and the current source is controlled by a pulse method. Depending on the current load, the predetermined motor speed results in a predetermined duty factor of the control current or a predetermined pump flow. However, the load during one motor rotation is not constant, because it is an angle dependent load, that is, it is a hydraulic pump of a vehicle braking system. The ripple signal is read out from the voltage potential present in the motor in one rotation and the periodicity is evaluated. Therefore, it is possible to set a constant rotational speed by adaptation of each position dependency of the duty factor of the control pulse in case of an event occurring periodically, which contributes to noise reduction and thereby increases driving comfort.

However, in the methods and devices known from the prior art, in order to transfer the relatively small hydraulic volumes of the pump motor or to set small minimum braking pressures, the pump motor is only controlled for a short time, . The high inrush currents associated with them cause current and voltage fluctuations in the entire vehicle electrical system, which can lead to disruption to other consumers of the vehicle electrical system, or to reliance on other consumers, thus requiring a sophisticated design do. Also, each position sensor is often required to determine the current angular position of the motor and pump.

Accordingly, the task addressed by the present invention is to provide a method of overcoming the above disadvantages.

This problem is solved by a method of transferring a metering hydraulic volume in a vehicle braking system by an electrically driven motor pump assembly according to claim 1 in accordance with the present invention.

The present invention relates to a method of transferring a metering hydraulic volume in an automotive braking system by means of an electrically driven motor pump assembly wherein the mechanical pump of the motor pump assembly is driven by an electric motor of the motor pump assembly, The motor current is detected and the transmission mode of the motor pump assembly is started as soon as the motor torque generated by the motor current exceeds the sum of the drag torque, the brake away torque, and the frictional torque of the motor pump assembly And the motor current decreases when the transfer mode starts. The method is distinguished by a motor current that is reduced to a value that terminates the delivery mode when a decrease in the motor current is detected after a specified time interval has elapsed.

This results in the advantage that the motor is not actuated immediately by the entire motor current, since the motor current is accompanied by a relatively slowly rising motor voltage ramp to the start of the motor. Thus, excessive overloading of the vehicle electrical system caused by current and voltage fluctuations and additional consumers connected to the vehicle electrical system is prevented. Therefore, since the voltage and current variations are substantially reduced by the method according to the present invention, these consumers can also be designed to be relatively simple and less robust with respect to voltage and current variations. Thus, the overall design of the electric vehicle infrastructure can be simplified.

The reduction of the motor current is necessarily an effect that occurs when the transfer mode starts, because the motor torque applied at the start of the transfer mode decreases by the amount of the brake away torque. Thus, the motor current no longer carries the motor voltage ramp once the transfer mode begins or once the electromotive force begins.

The motor current is preferably detected by the brush and armature of the electric motor. If this is a brushless electric motor, the motor current can also be exclusively detected by the armature.

When the motor current is detected and thus the start of the transfer mode is detected after the lapse of the prescribed time interval, the transfer voltage can not be maintained and thus the motor voltage is again reduced to a value which also ends the transfer mode, The hydraulic volume can be measured relatively accurately. The reduction of the motor voltage also results in a reduction of the motor current, and if this motor current is too low to maintain the transfer mode, the transfer mode is immediately terminated.

In particular, the motor voltage is reduced to a value of 0V. This ensures a fast and reliable termination of the delivery mode.

The prescribed time interval may be defined as being fixed and unchanged or adapted. The longer the duration of the time interval is, the larger the volume of the delivered hydraulic volume is.

Preferably, the electrical control of the motor pump assembly is defined as being performed by a pulse width modulation scheme, in particular by a clock frequency of at least 1 kHz. Pulse width modulation control is an option for variable control of electrical consumers that is relatively simple and inexpensive. The higher the clock frequency of the control, the more sensitively it is implemented. Clock frequencies above 1 kHz have been proven to be sufficient to ensure quiet and smooth start of the transfer mode.

In addition, it is preferable that the time interval is extremely small. This results in the advantage that only a very small hydraulic volume is delivered, as soon as the delivery mode is started again. As a result, ultimately, the delivered hydraulic volume can be measured very accurately.

It is defined that a decrease is detected by observing the gradient of the motor current. This leads to the advantage that the reduction can be reliably detected in a simple manner based on the sign of the gradient and also in the case of relatively low motor currents. In this case, the occurrence of a negative gradient indicates a decrease in the motor current. In this case, in particular, a negative gradient is defined to be formed and observed by an electrical circuit arrangement designed for this purpose. This circuit arrangement can be designed, for example, as a relative current measurement circuit, which is in principle also used in a number of known braking control devices for detecting motor currents. In addition, however, it has been proven advantageous to provide a low resistance measurement resistor to the relative current measurement circuit, which can also be designed as a conductor path resistance to reduce cost. The gradient may also be formed in a hardware-based manner, rather than by a software algorithm, and in the latter case an interrupt occurs immediately after the gradient is formed and the gradient is sent to a software algorithm designed for this purpose.

It is further defined that this method is performed only in a single brake circuit of a multi-circuit vehicle braking system. This results in an advantage that the generated vehicle deceleration is reduced or substantially in the case of a dual circuit vehicle braking system. Thus, vehicle deceleration can be set more sensitively and can be controlled more accurately.

In particular, the shut-off valve and the switchover valve of the brake circuit of the multi-circuit vehicle braking system, in which the electric motor of the motor pump assembly is not actuated by the motor voltage ramp, are also defined as open. Therefore, it is ensured that the braking pressure is not built up in this brake circuit, and therefore the vehicle is not decelerated. This also improves the sensitive control of vehicle deceleration. Particularly in the case of the so-called diagonal division of the brake circuits of a dual circuit vehicle braking system, the additional advantage is that the generation of alternating torques and hence the transmission of the vibrations to the steering can be prevented.

The method according to the invention is preferably distinguished by the motor and / or the respective position of the pump, which is determined by the motor voltage, the motor current and the predetermined hydraulic pressure in the vehicle braking system. The energy input to the motor pump assembly can be easily determined via the motor current and the motor voltage when the transfer mode begins. Therefore, in consideration of the hydraulic pressure prevailing in the vehicle braking system, the change of each position of the motor or the pump can be determined, so that the current angular position can ultimately be determined based on the finally known angular position. This results in the advantage that each position sensor is not required, which helps to reduce manufacturing complexity and costs for the motor pump assembly.

In a more preferred embodiment of the present invention, the delivered hydraulic volume is defined to be determined from the angular position of the motor and / or the pump and the defined time interval. Since each change in position of the motor or pump is associated with the delivery mode of the motor pump assembly, the delivered hydraulic volume can be adjusted, for example, by a corresponding feature curve, in particular considering the absolute start angle position and the absolute final angle position, Can be determined from a change in position in a reliable and simple manner.

It is also advantageous that the method is repeated continuously until the prescribed hydraulic setpoint pressure is reached. Thus, the required setpoint pressure can be continuously built up in a relatively sensitive manner in a plurality of successive steps, since the delivered hydraulic volume can in each case be measured in a sensitive manner. This is particularly beneficial for all vehicle systems designed to be comfort oriented, although requiring only a slight pressure change. One example of such is the distance and speed control system.

The invention also relates to a vehicle braking system comprising at least one hydraulic brake circuit having at least one electronic control unit and an electric motor pump assembly, wherein the electric motor of the motor pump assembly drives a mechanical pump of the motor pump assembly, The control unit operates on the electric motor of the motor pump assembly by the rising motor voltage ramp, the control unit detects the motor current, and the transfer mode of the motor pump assembly is such that the motor torque generated by the motor current The drag torque, the brake away torque, and the friction torque, and the motor current decreases when the transfer mode starts. The vehicle braking system is distinguished by a control unit that reduces the motor voltage to a value that terminates the delivery mode when a decrease in the motor current is detected after a specified time interval has elapsed. Thus, the vehicle braking system according to the present invention has all the means necessary to carry out the method according to the invention. Considering that the vehicle braking system according to the present invention reduces the motor voltage to a value that terminates the transfer mode of the motor pump assembly when a decrease in the motor current is detected, the above-described advantages result.

The vehicle braking system preferably implements the method according to the invention.

Further preferred embodiments will become apparent from the following description of exemplary embodiments with reference to dependent claims and drawings.

In the drawings:
1 shows the process of motor voltage and motor current during the motor voltage ramp up to the start and end of the transfer mode.
Figure 2 shows a flowchart of one possible sequence of the method according to the invention.

Figure 1 (a) shows current I and voltage U over time t, where curve 11 describes the motor voltage and curve 12 illustrates the motor current. In this case, the movement in accordance with the motor voltage ramp starts at time t ₀ and is depicted as the rise of curve 11 in the interval of t ₀ to t ₂ . The motor current also rises in curve 12 in proportion to the rise of curve 11, but only in the interval from t ₀ to t ₁ . At time t _1, the generated motor torque not to exceed the sum of the motor pump assembly, the drag torque, breakaway torque, and friction torque, thereby starting the transfer mode of the motor pump assembly. This ultimately results in a breakdown of the motor current at time t ₁ . Since the gradient of the motor current is formed and observed, the breakdown or reduction of the motor current is detected based on the sign change of the gradient, and the sign of the gradient is now negative. Immediately after the motor current reduction is detected, that is, after a finite time interval has elapsed, the motor voltage is reduced to a value of 0V at time t ₂ to terminate the transfer mode. The motor current can not directly lead to such a reduction of sudden motor voltage it does not decrease to a value of 0V until time (t _3). The curve 13 depicting the gradient of the motor current is shown in Figure 1 (b). As is evident, the gradient has a constant positive value while the motor current is constantly rising. However, at time t ₁ when the motor current breaks down, the gradient changes sign and is now negative. This is how the breakdown or reduction of the motor current is detected.

Figure 2 shows a flowchart of one possible sequence of the method according to the invention. In step 201 of the method, the motor of the motor pump assembly is operated by a rising motor voltage ramp. In step 202, the motor current induced by the motor voltage ramp is continuously and continuously detected. At step 203, the increasing motor voltage and the increasing motor current lead to an increasing motor torque. In step 204 of the method, a gradient of the motor current is formed, and in step 205, the gradient of the motor current is continuously and constantly observed. The generated motor torque exceeds the sum of the drag torque, the brake away torque, and the friction torque of the motor pump assembly in step 206 of the method, so that in step 207 the transfer mode of the motor pump assembly is initiated. The start of the delivery mode is detected by continuous observation of the gradient of the motor current, which occurs at step 205, and as a result at step 208, the motor voltage is reduced to a value of 0V. Subsequently, the delivery mode of the motor pump assembly is terminated at step 209. In step 210, the change in each position of the electric motor or pump is determined from the motor current, the motor voltage, and the hydraulic pressure in the vehicle braking system, and then the most recent absolute angular position is taken into consideration The current absolute angular position is determined. In step 211 of the following method, the delivered hydraulic volume is determined, taking into account the starting angular position and the final angular position of the pump or motor due to the delivery method of the pump depending on each position. Finally, at step 212, the current pressure in the vehicle braking system is compared to the setpoint pressure to be built. If the setpoint pressure has been reached, the method ends at step 213. However, if the setpoint pressure has not yet been reached, the method is run again at step 201 via step 214.

Claims (11)

A method for transferring a metering hydraulic volume in a vehicle braking system by an electrically driven motor pump assembly,
A mechanical pump of the motor pump assembly is driven by an electric motor of the motor pump assembly,
The electric motor is actuated by a rising motor voltage ramp and the motor current 12 is detected and the motor torque generated by the motor current 12 is determined by the drag torque of the motor pump assembly, Torque, and friction torque, the transfer mode of the motor pump assembly begins, and
The motor current 12 decreases when the delivery mode begins,
Characterized in that the motor voltage (11) is reduced to a value which terminates the transfer mode when a decrease in the motor current (12) is detected after a specified time interval has elapsed. The method according to claim 1,
Characterized in that the electrical control of the motor pump assembly is carried out in a pulse width modulation manner, in particular using a clock frequency of at least 1 kHz. 3. The method according to claim 1 or 2,
Wherein said time interval is negligible. 4. The method according to any one of claims 1 to 3,
Characterized in that the reduction is detected by observing a gradient (13) of the motor current (12). 5. The method according to any one of claims 1 to 4,
Characterized in that the method is carried out only in a single brake circuit of a multi-circuit vehicle braking system. 6. The method of claim 5,
Wherein the shut-off valve and the switchover valve of the brake circuit of the multi-circuit vehicle braking system, wherein the electric motor of the motor pump assembly is not actuated by the motor voltage ramp, are opened. 7. The method according to any one of claims 1 to 6,
Characterized in that each position of the motor and / or the pump is determined by the motor voltage (11), the motor current (12) and the predetermined hydraulic pressure in the vehicle braking system Way. 8. The method of claim 7,
Wherein said delivered hydraulic volume is determined from each position of said motor and / or said pump and said defined time interval. 9. The method according to any one of claims 1 to 8,
Wherein the method is repeated continuously until a prescribed hydraulic setpoint pressure is reached. ≪ Desc / Clms Page number 13 > A vehicle braking system comprising at least one hydraulic brake circuit having at least one electronic control unit and an electric motor pump assembly,
An electric motor of the motor pump assembly drives a mechanical pump of the motor pump assembly,
Wherein the control unit operates on an electric motor of the motor pump assembly by a rising motor voltage ramp, the control unit detects the motor current (12) and the motor torque generated by the motor current (12) As soon as the sum of the drag torque, the brake away torque, and the friction torque of the motor pump assembly is exceeded, the transfer mode of the motor pump assembly commences,
The motor current 12 decreases when the delivery mode begins,
Characterized in that the control unit reduces the motor voltage (11) to a value which terminates the transfer mode when a decrease in the motor current (12) is detected after a specified time interval has elapsed. 11. The method of claim 10,
The vehicle braking system according to any one of claims 1 to 9, wherein the vehicle braking system executes the method according to any one of claims 1 to 9.

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